The diagnosis of oral cancer should be made as soon as possible in order to improve the chances of patient survival. In addition to self-examination of the oral cavity, clinical examination by a professional is essential for early detection of this disease, whose appearance may vary considerably. 

Cancer is a disease caused by a group of cells that multiply uncontrollably and autonomously. It may involve invasion of nearby tissues and of tissues farther away, known as metastasis, which is the main cause of death from cancer. 

It is estimated that in 2018 there will have been 18.1 million new cases of cancer and 9.6 million deaths from the disease worldwide. In both sexes combined, lung cancer is the most commonly diagnosed and the leading cause of death from cancer, closely followed by diagnoses of female breast cancer, prostate cancer and colorectal cancer. By mortality, lung cancer is followed by colorectal cancer, stomach cancer, and liver cancer. 

In Spain, the most commonly diagnosed tumours in 2015 in both sexes were colorectal, prostate, lung, breast and bladder tumours, with lung and colorectal tumours showing by far the highest mortality rates. In addition, 6,670 new cases of lip, oral and pharyngeal cancer were diagnosed, representing about 2.7% of all cases of cancer diagnosed in both sexes. Also, and according to the same study from which the previous data are derived, in 2014 there were 2,331 deaths caused by oral and pharyngeal tumours in both sexes. Likewise, the relative five-year survival rate for oral cancer is about 50%. 

Oral cancer can affect any part of the oral cavity and is most frequently located along the sides of the tongue and on the floor of the mouth, although it can also appear in other structures such as the oropharynx, the hard and soft palate, the vestibular and buccal mucosa, the gums, or the inside of the lips. 

The most common lesions are usually ulcerated with indurated edges, followed by exophytic lesions. 

RISK FACTORS AND MORPHOLOGY OF ORAL CANCER 

The main risk factors are, in order: tobacco smoking, drinking alcohol, head and neck irradiation, iron and vitamin A deficiencies, human papillomavirus (HPV), Candida infections, and immunosuppression. Other factors that may be associated with the appearance of oral cancer are: a diet poor in fruits, vegetables and antioxidants in general; individuals with poor oral hygiene, teeth in poor condition or rarely visiting the dentist; a family history of cancer, and sociological factors such as poverty, crowded living conditions and marginalisation. 

Tobacco contains over 60 carcinogenic products of combustion which are able to bind with and alter DNA. In addition, it increases oxidative stress in tissues, and thus the release of free radical species, which damage proteins, lipids, carbohydrates and the DNA itself. 

Studies have shown that the risk of oral cancer in smokers is three to five times greater than in non-smokers, that the effect is dose-dependent, and that this multiplies dramatically if associated with drinking alcohol. 

The lesions in the mouth that show the greatest risk of becoming malignant are leukoplakias, which are described as growing whitish plaques that form part of the epithelium, and that cannot be detached by scraping. They are mainly attributed to tobacco smoking and are precursors to oral cancer in approximately 10% of all cases. 

The clinical appearance of oral cancer is highly variable, depending on how long the tumour has had to develop. The size may range from a few millimetres to several centimetres. There are generally considered to be certain early forms, and other advanced ones. 

The early forms are cancers that are most likely preceded by leukoplastic precancerous lesions (appearing as white spots), erythroplastic lesions (red spots) and erythroleukoplasic lesions (spots with red and white areas). The advanced forms would correspond to ulcerated or endophytic lesions, exophytic lesions or mixed lesions. 

DIAGNOSIS 

The diagnosis of oral cancer should be carried out as soon as possible, since the chances of survival improve considerably with early detection. Firstly, self-examination by the patient and examination at the clinic by a professional is essential. There are also non-invasive diagnostic techniques, such as vital staining and light-based methods. The definitive diagnosis should always be made by incisional or excisional biopsy. 

Self-examinations should be carried out after oral hygiene and in front of a mirror under good lighting. Start with your mouth closed and check your lips. Next, hold your lip with your fingertips and turn it outwards, observing it carefully. In this position, inspect the teeth and gums in occlusion with the jaws shut, and then examine the inside of the teeth and gums with jaws open. 

Also, in this position, move and examine the inner side of the cheeks. Next, raise the tip of the tongue towards the palate and towards the sides and look at the edges and the lower part—the floor of the mouth. You can assist this by holding the tip of your tongue with your fingers or with some gauze. Then stick your tongue out to observe the top and back and tilt your head back to examine the palate. 

Finally, it is recommendable that you feel all the parts of the oral cavity with your fingers, searching for any wounds or sores, changes in colour, red, white or dark spots, and any lumps on the lips and gums, cheeks, tongue, palate or any part of the mouth. 

Keep an eye on high risk areas, such as the sides and the underside of the tongue, the floor of the mouth and the hard and soft palate. In case there are lesions that do not heal once the cause has disappeared, and where they have developed over more than two weeks, particular attention should be paid, scheduling a biopsy for definitive diagnosis and/or remission of the lesion. 

PREVENTION 

As always, prevention is key to the management of any disease. Since smoking is the main risk factor for this disease, giving up smoking is always recommended. There are pharmacological therapies that may be considered in order to contribute to cutting down or quitting the habit. 

However, other measures such as setting up regular oral examinations can be very helpful. During these visits, a professional must connect with the patient, inform them of the risks smoking poses to their oral and general health, and try to motivate the patient through individual counselling. 

In this regard, the motivational interview as developed by Miller and Rollnick may be very helpful, as is the AAR programme - Ask, Advise & Refer - which has recently been proposed for the management of these patients. Drinking habits can also be handled in this way. Another very important aspect is diet. 

Daily consumption of fruit and vegetables can halve the risk of oral cancer. In addition to the antioxidants present in these foods, dietary fibre, vitamin A and its precursors, vitamins E and C, and folic acid have been identified as having a protective role against oral cancer. 

TREATMENT 

In the foreseeable future, the methods of oral cancer treatment include surgery, radiation therapy, chemotherapy and immunotherapy. In general, treatment in the initial stages should be made through a single technique, either surgery or radiation therapy. 

In advanced stages, combined therapies are necessary, generally surgery followed by radiation therapy and chemotherapy. Inoperable tumours are usually treated with combined chemotherapy and radiation therapy. The choice of treatment is made by a multidisciplinary head & neck tumour team, taking into account the stage of the tumour, the patient's general condition and co-morbidities, as well as the patient's wishes. 

CONCLUSION 

Controlling the risk factors associated with the onset of oral cancer and the early detection of the candidate lesions can greatly improve the expectations of patient survival, as well as their quality of life.